This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Acronyms used in this application or the drawings are defined below.
In 3GPP Rel-10 Carrier Aggregation (CA), two or more Component Carriers (CCs) are aggregated in order to support wider transmission bandwidths up to 100 MHz. A UE may simultaneously receive or transmit on one or multiple CCs, depending on its capabilities.
CA operation uses a number of serving cells, one for each CC. The Primary Serving Cell (PCell) is served by the Primary Component Carrier (PCC) and handles the Radio Resource Control (RRC) Connection with the UE. One or more Secondary Serving Cells (SCells) are served by the Secondary Component Carriers (SCCs) and provide the additional transmission bandwidth.
CA operation may be thought of as one aspect of dual connectivity. According to 3GPP TR 36.842 V12.0.0 (2013-12), Section 7.1, the term “dual connectivity” is used to refer to operation where a given UE consumes radio resources provided by at least two different network points connected with non-ideal backhaul. Furthermore, each eNB involved in dual connectivity for a UE may assume different roles. Those roles do not necessarily depend on the eNB's power class and can vary among UEs. See Section 7 of 3GPP TR 36.842 for additional description regarding dual connectivity.
The Rel-10 3GPP specification supports CA operation only in a scenario where the PCell and SCell(s) are co-located in the same eNB. It would be beneficial to improve on this scenario.